Method of manufacturing aluminum alloy cylinders and cylinder liners for internal combustion engines

ABSTRACT

A method of manufacturing an aluminum alloy cylinder or cylinder liner for an internal combustion engine, wherein an integral layer of carbonaceous material is formed on at least a portion of the inner surface of the cylinder or cylinder liner to provide that portion with an increased resistance to frictional wear.

United States Patent 11 1 Kaneko et al.

[4 1 Sept. 9, 1975 [22] Filed: Feb. 1. I974 121 I App]. No: 438,695

Related [1.5. Application Data [631 (ontinuationinpzirt of Ser. No. 262L071. June 3() 1972 abandoned.

[30} Foreign Application Priority Data Jun. 1-'l 1972 Japan 476420 [52] US. Cl. .1 164/97; 164/120; 164/132;

29/1564 WL; 123/193 C; 92/169 [51) Int. Cl 322d 19/00; 822d 27/12 [58] Field of Search .1 29/1564 WL, 527.3; 164/120, 112 132. 97, 75; 92/169; 123/193 C [56] References Cited UNITED STATES PATENTS 19381257 12/1933 Jones 164/120 1081424 4/1963 Bauer Y v 164/112 3,744,548 7/ 1973 lkcdu ct al. 164/97 Primary ExamiIwrCi W. Lzmham Assistant blnmziner-Dan Ci Crane Allorney, Agwm or FirrrzStevens Davis, Miller & Mosher [57] ABSTRACT A method of manufacturing an aluminum alloy cylinder or cylinder liner for an internal combustion engine wherein an integral layer of carbonaceous material is formed on at least a portion of the inner surface of the cylinder or cylinder liner to provide that portion with an increased resistance to frictional wear.

6 Claims, 5 Drawing Figures PATENTEU SEP 9 I975 SHEET 1 Bf 2 FIGJ METHOD OF MANUFACTURING ALUMINUM ALLOY CYLINDERS AND CYLINDER LINERS FOR INTERNAL COMBUSTION ENGINES RELATED APPLICATION This application is a continuation-in-part of appli cants copending application Ser. No. 268,071 filed on June 30, I972, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a method of manufacturing an improved cylinder or cylinder liner for an internal combustion engine, and more particularly to a method of manufacturing such cylinder or cylinder liner made of an aluminum alloy and having an integral layer of carbonaceous material formed on at least a portion of the inner surface thereof.

For an internal combustion engine known in the art, there has been provided a cylinder made of cast iron or a cylinder made of an aluminum alloy into which a cylinder liner made of cast iron is inserted. There has also been developed a cylinder made ofa high silicon aluminum alloy and having an inner surface subjected to a special surface treatment.

It is well recognized that an internal combustion engine cylinder should be made of such material as is highly resistant to wear, is light in weight and has a good thermal conductivity and a good machinability. But the cast iron cylinder known in the art is heavy in weight and has a poor thermal conductivity, though it has a relatively good wear resistance. The aluminum alloy cylinder of the prior art is relatively light in weight and has a relatively good thermal conductivity, but it is liable to wear. The high silicon aluminum alloy cylinder has a poor machinability due to the hardness of the silicon contained therein, and requires plenty of time and labor for the treatment of the inner surface thereof, resulting in high costs of manufacture.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method of manufacturing an improved internal combustion engine cylinder or cylinder liner which is more resistant to wear, is lighter in weight, has a better thermal conductivity and machinability, and is less expensive to manufacture, than any such product known in the art.

It is another object of this invention to provide a method of manufacturing an aluminum alloy cylinder or cylinder liner for an internal combustion engine wherein an integral layer of carbonaceous material is formed on at least a portion of the inner surface of the cylinder or cylinder liner.

According to a salient feature of this invention, use is made of a cylindrical reticulated basket disposed to surround a cylindrical core and define a cylindrical hollow space therebetween into which a supply of carbonaceous material, such as carbon, graphite or a mixture of both, is furnished. This carbonaceous material is integrally joined with a molten mass of an aluminum alloy poured into a cylindrical hollow space or cavity defined between the basket and the lower half ofa mold when the basket, together with the core, is placed in the lower mold half.

The method of this invention comprises supplying carbonaceous material. such as carbon, graphite or a mixture of both, into a cylindrical hollow space defined between a cylindrical core and a cylindrical reticulated basket disposed to surround the core; placing the core and the basket containing the carbonaceous material together into the lower half of a mold in vertical alignment therewith, whereby a cylindrical hollow space or cavity is defined between the basket and the lower mold half; pouring a molten mass ofan aluminum alloy into the cylindrical cavity encircling the basket; lowering the upper half of the mold under pressure onto the molten aluminum alloy to compress the molten aluminum alloy, whereby a cylindrical intermediate product having an integral inner surface layer formed by the carbonaceous material is produced; withdrawing the intermediate product from the mold together with the core; separating the core from the intermediate product; and machining the intermediate product to obtain a final product.

The cylinder or cylinder liner manufactured by the method of this invention is highly resistant to frictional wear on the inner surface thereof, because the integral layer of carbonaceous material, whether carbon, graphite or a mixture of both, does not only provide a good lubricating function itself, but its porous structure is also useful in promoting lubrication as its pores serve to hold a lubricant.

Both carbon and graphite are also a good conductor of heat and have a high thermal resistance. Moreover, an aluminum alloy has a better thermal conductivity than any type of cast iron. Therefore, the cylinder or cylinder liner manufactured by the method of this invention provides an excellent cooling efficiency, which is one of the important requisites for an internal combustion engine. Thus, the cylinder or cylinder liner manufactured by the method of this invention is not liable to any serious seizure even during the operation of the engine at a high speed, nor does it undergo any serious scuffing when the engine has been started from cold.

Moreover, as an aluminum alloy has a smaller specific gravity than cast iron, the cylinder or cylinder liner according to this invention is less heavy than any cast iron cylinder or cylinder liner known in the art.

Furthermore, it is very easy to machine the inner surface of the cylinder or cylinder liner manufactured according to this invention because it is formed from carbonaceous material, such as carbon, graphite or a mixture of both, and the chips of such carbonaceous material produced during the machining work are easily broken. On the other hand, the high silicon aluminum alloy cylinder known in the art requires considerably more time and labor for the machining of its inner surface because silicon is a very hard material, though it also serves as a chip breaker. Moreover, the silicon contained in the cylinder causes, due to its hardness, a very quick wear of a cutting tool employed for the machining work.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view, partly in section, of a cylinder liner manufactured by the method of this invention;

FIG. 2 is a photograph showing a microscopic structure of a section of the cylinder liner manufactured according to Example No. 2 which will hereinafter be described;

FIG. 3 is a photograph showing a microscopic structure of a section of the cylinder liner according to Example No. 3 which will hereinafter be described;

FIG. 4 is a schematic illustration of a process for manufacturing a cylinder liner by the method of this invention; and

FIG. 5 is a general longitudinal sectional view of a semi-final product manufactured by the process illustrated in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 4 of the drawings, a brief description will first be made of one example of apparatus which may be employed to carry out the method of this invention. The apparatus illustrated in FIG. 4 comprises a lower or female mold half 11 mounted on the bolster of a press; a knock-out rod 13 provided in coaxial relation to the lower mold half 11 and adapted for axial movement relative to the lower mold half 11 to knock out a casting from the lower mold half 11 when it is moved upwardly; a cylindrical splittable core 12 composed of six separate elements 120 fastened together by a ring 12b and encircling a center element 12a secured to the top of the knockout rod 13; and an upper mold half 17 positioned vertically movably to or away from the lower mold half II and adapted to press down on a molten mass 16 of an aluminum alloy in the lower mold half II when it is lowered into the lower mold half 11 and actuated by the press.

A preferred embodiment of the method of this invention will be described with reference to the sequence of operation illustrated in FIG. 4.

I. As shown at a in FIG. 4, a cylindrical reticulated basket 14 having suitably sized meshes and having an open top and an annular closed bottom encircling the core 12 is inserted over the core 12 with its annular bottom brought into flush alignment with the bottom ofthe core I2 or the top of the knock-out rod 13 and defines a cylindrical hollow space around the core I2. Carbonaceous material 15, such as carbon, graphite or a mixture of both, is fed by a spoon or like means into the hollow space between the core 12 and the basket 14 through the open top of the basket I4 until the basket I4 is fully filled with the carbonaceous material 15. Then, the knock-out rod 13 is lowered to bring down the core 12 and the basket 14 to a predetermined position within the lower mold half I I.

2. A molten mass 16 of an aluminum alloy is poured into the lower mold half II until it fully fills a cylindrical hollow space defined between the peripheral surfaces of the core I2 and the basket 14 and the inner surface of the lower mold half 11 as shown at b in FIG. 4.

3. The upper mold half 17 is lowered into the lower mold half 11 to compress the molten aluminum alloy mass 16 as shown in FIG. 4 at c. During this step of operation. the aluminum alloy solidifies and is joined with the carbonaceous material in the basket 14 because of the reticulated structure of the basket 14, whereby the carbonaceous material I5, together with the basket 14, forms an integral inner surface layer of a cylindrical aluminum alloy casting. Then, the upper mold half I7 is removed from the lower mold half I].

4. Then, the knock-out rod 13 is raised to knock out a product 19 as cast from the lower mold half II as a beginning stage of this operation is indicated at d in FIG. 4.

5. After the product 19 as cast is completely withdrawn from the lower mold half 11 and the knock-out rod 13 is stopped, a supporting plate or plates 18 are inserted between the upper end of the lower mold half 11 and the lower end of the product I9 and placed on the upper end of the lower mold half 11 as shown in FIG. 4 at 2. Then. the knockout rod 13 is lowered.

6. As the knock-out rod 13 is lowered, the center element 12a of the core 12 integrally connected to the knock-out rod 13 is withdrawn and separated from the other elements of the core 12, while the as cast product 19 is left on the supporting plate 18 as shown in FIG. 4 at f. The ring 12b is removed from the core elements 12c, and the core elements 12c are stricken by a hammer or like means and detached from the as cast product 19. The as cast product 19 may thereafter be subjected to heat treatment and machine finishing by conventional methods as needed and a cylinder liner is obtained.

Description will now be made of several examples illustrating in a non-restrictive manner how the princi ples of this invention may be reduced to practice.

EXAMPLE NO. 1

An aluminum alloy cylinder liner as shown in FIG. I is manufactured by the process illustrated in FIG. 4 by using a ZOO-mesh cylindrical reticulated basket made of stainless steel wire. Hollow carbon balls having a di ameter of about 200 u are substantially uniformly fed into the cylindrical hollow space defined between the core and the reticulated basket and the core and the basket are placed in the lower mold half. A molten mass of an ACSB aluminum alloy is then poured into the hollow cylindrical space defined between the peripheral surfaces of the core and the basket and the inner surface of the lower mold half. Immediately thereafter. the upper mold half is lowered into the lower mold half to act on the molten alloy, and a pressure of 1,000 kg/cm is applied to the upper mold half for 50 seconds by the press to compress the molten alloy, whereby a cylindrical aluminum alloy casting having an integral inner surface layer formed by the carbon balls is produced. The casting is then worked on a machine tool to receive the necessary finish to obtain a cylinder liner as shown in FIG. I.

In this way, a total of eight cylinder liners are manufactured and a wear resistance test is conducted on these cylinder liners. The test is conducted by using a V-type eight-cylinder 3,000 cc cylinder block made of an aluminum alloy. pistons made of an AC8B aluminum alloy and piston rings made of cast iron. The test is continued for about six to eight hours a day until a total of 100 hours with a rotational speed of 4,500 rpm. and an absorption horsepower of HP.

The results of the test indicate that the amount of wear on the inner surfaces of the cylinder liners is as small as about Sp. to 8p as diametrically measured by an air micrometer at both the upper and lower portions of the cylinder liners. Moreover, the test shows that none of the cylinder liners indicates any scuffing that would often occur with the cylinder liners manufactured according to the prior art when an engine is started from cold. but the cylinder liners manufactured by the method of this invention are found to be highly resistant to wear even during the start-up of engine operation.

EXAMPLE NO. 2

Eight cylinder liners are manufactured by the same method as described in EXAMPLE No. 1, except that hollow carbon balls having a diameter of about 100p. are used to form the inner surface layers l of the liners and that a pressure of 1,200 kg/cm is applied to compress the molten aluminum alloy.

The test of EXAMPLE No. l is repeated under the same conditions by using the same test equipment. The results of the test show that the amount of wear on the inner surfaces of the cylinder liners is as small as about 3 4. to 6;; as diametrically measured by an air micrometer at both the upper and lower portions of the cylinder liners. The test also proves that the cylinder liners manufactured by the method of this invention are highly resistant to wear even during the start-up of engine operation. The microstructure of a section of one of the cylinder liners manufactured as described in this Example is shown in the photograph of FIG. 2, in which round substances 2 are carbon particles.

EXAMPLE NO. 3

Eight cylinder liners are manufactured by the same method as described in EXAMPLE No. 1, except that a substantially uniform mixture of hollow spherical carbon particles having a diameter of about 100p. and graphite flakes having an approximate length ranging from 50;; to 300 is used to form the inner surface layers l of the liners and that a pressure of 1,200 kg/cm is applied for one minute to compress the molten aluminum alloy.

The test of EXAMPLE No. l is repeated under the same conditions by using the same test equipment. The test results indicate that the amount of wear on the inner surfaces of the cylinder liners manufactured according to this Example is as small as about 3p. to 6,1. as diametrically measured by an air micrometer at both the upper and lower portions of the liners. The test also proves that the cylinder liners manufactured by the method of this invention are highly resistant to wear even during the start-up of engine operation. The microstructure of a section of one of the cylinder liners manufactured as described in this Example is shown in the photograph of FIG. 3, in which round substances 3 are carbon particles and flaky substances 4 are graphite.

EXAMPLE NO. 4

Eight cylinder liners are manufactured by the same method as described in EXAMPLE No. I, except that the liners are made of an ACSA aluminum alloy and are each formed with an inner surface layer 1 of graphite flakes having an approximate length ranging from 70pm to 30011., and that a pressure of 1,500 kg/cm is applied for one minute to compress the molten aluminum alloy.

The test of EXAMPLE No. I is repeated under the same conditions by using the same test equipment as described in EXAMPLE No. l. The results of the test indicate that the amount of wear on the inner surfaces of the cylinder liners manufactured according to this Example is as small as about 3,4. to 7 1. as diametrically measured by an air micrometer at both the upper and lower portions of the cylinder liners. The test results also show that the cylinder liners manufactured by the method of this invention are highly resistant to wear even during the start-up of engine operation.

Attention is now directed to the results of the tests conducted to compare the cylinder liners manufactured according to the foregoing examples of this invention with cylinder liners known in the prior art. Cast iron cylinder liners of the same shape and size are manufactured for the purpose of comparison with respect to the resistance of their inner surfaces to frictional wear against the results obtained on the cylinder liners according to.this invention as described in the foregoing examples. These cast iron cylinder liners are tested by using a V-type eight-cylinder 3,000 cc cylinder block, pistons made of an ACBB aluminum alloy and chromium plated piston rings made of cast iron under the same conditions (i.e., test duration) as those described in the foregoing examples. The test results indicate that the amount of wear on the inner surfaces of these cast iron liners ranges approximately from 10p. to 15 as diametrically measured by an air micrometer of the same type as used in the foregoing examples No. 1 through No. 4. It will thus be noted that the cylinder liners manufactured by the method of this invention have about twice as good a resistance to frictional wear as, or in many instances even better than, the cast iron cylinder liners which are typical of the prior art.

While ACSA and ACSA aluminum alloys are used in the foregoing examples to manufacture cylinder liners according to this invention, it should be understood that any other type of an aluminum alloy suitable for casting purpose may be used to manufacture cylinders and cylinder liners by the method of this invention, if a proper selection is made depending upon the mechanical strength, thermal expansibility and other conditions required of a final product. It is also to be understood that the reference in the foregoing description to spherical hollow carbon particles and graphite flakes does not preclude use of any other shape of such carbonaceous material to form the inner surface layer of an aluminum alloy cylinder or cylinder liner within the scope of this invention. It should, moreover, be noted that such carbonaceous material is not required to have any special physical properties, but may be any ordinary product available on the market. It should also be understood that according to this invention, a layer of carbonaceous material may be either provided only on that portion of a cylinder or cylinder liner which may be subjected to frictional contact with a coacting piston, or alternatively all over the inner surface of the cylinder or cylinder liner.

Although in the foregoing description of the preferred embodiment and examples of this invention reference has only been made to the manufacture of cylinder liners, it will be apparent that the principles of this invention is equally applicable to the manufacture of cylinders having an inner surface layer of carbonaceous material which is substantially as strong against frictional wear as testified in the examples hereinbefore described.

While this invention has been described with reference to a preferred embodiment and several examples, it should be understood that various modifications or changes may be made by anybody of ordinary skill in the art without departing from the scope of the invention which is defined by the appended claims.

What is claimed is:

1. In a method for manufacturing an aluminum alloy cylinder or cylinder liner for an internal combustion engine, wherein a molten mass of an aluminum alloy is poured into a cylindrical mold cavity provided in the lower half of a mold, the upper half of said mold is placed on said molten mass and a downward pressure is applied onto said upper half of said mold, said cylinder or cylinder liner having an inner surface layer of carbonaceous material which provides an increased wear resistance, the improvement which comprises:

placing a cylindrical reticulated basket of a desired diameter around a cylinder core in a coaxial relation therewith to define a hollow cylindrical space of a desired diameter between said core and said basket;

supplying said carbonaceous material into said hollow cylindrical space, and

placing said core and said basket together in said lower half of said mold in a coaxial relation therewith to define said mold cavity between said basket and said lower half of said mold. said molten mass being poured into said mold cavity and flowing into said basket, whereby said carbonaceous material is embedded in said molten mass to form said inner surface layer having a desired thickness.

2. The method of claim 1 wherein said pressure is at least 1,000 kg/cm and applied to said upper half of said mold for at least 50 seconds.

3. The method of claim I wherein said reticulated basket is made of stainless steel wire and has approximately 200 meshes per inch.

4. The method of claim 1 wherein said carbonaceous material comprises spherical carbon particles having a diameter ranging approximately from 100;; to 200p 5. The method of claim 1 wherein said carbonaceous material comprises graphite flakes having a length ranging approximately from to 300p.

6. The method of claim 1 wherein said carbonaceous material comprises a mixture of spherical carbon particles having a diameter of approximately p and graphite flakes having a length ranging approximately from 50p. to 300p. 

1. In a method for manufacturing an aluminum alloy cylinder or cylinder liner for an internal combustion engine, wherein a molten mass of an aluminum alloy is poured into a cylindrical mold cavity provided in the lower half of a mold, the upper half of said mold is placed on said molten mass and a downward pressure is applied onto said upper half of said mold, said cylinder or cylinder liner having an inner surface layer of carbonaceous material which provides an increased wear resistance, the improvement which comprises: placing a cylindrical reticulated basket of a desired diameter around a cylinder core in a coaxial relation therewith to define a hollow cylindrical space of a desired diameter between said core and said basket; supplying said carbonaceous material into said hollow cylindrical space; and placing said core and said basket together in said lower half of said mold in a coaxial relation therewith to define said mold cavity between said basket and said lower half of said mold, said molten mass being poured into said mold cavity and flowing into said basket, whereby said carbonaceous material is embedded in said molten mass to form said inner surface layer having a desired thickness.
 2. The method of claim 1 wherein said pressure is at least 1, 000 kg/cm2 and applied to said upper half of said mold for at least 50 seconds.
 3. The method of claim 1 wherein said reticulated basket is made of stainless steel wire and has approximately 200 meshes per inch.
 4. The method of claim 1 wherein said carbonaceous material comprises spherical carbon particles having a diameter ranging approximately from 100 Mu to 200 Mu .
 5. The method of claim 1 wherein said carbonaceous material comprises graphite flakes having a length ranging approximately from 70 Mu to 300 Mu .
 6. The method of claim 1 wherein said carbonaceous material comprises a mixture of spherical carbon particles having a diameter of approximately 100 Mu and graphite flakes having a length ranging approximately from 50 Mu to 300 Mu . 